The present invention generally relates to spintronics materials and magnetic sensors. More specifically, the invention relates to magnetic nano-multilayers for magnetic sensors and the manufacturing method thereof.
The magnetic sensors are extensively applied in several areas such as the data storage, mechanical positioning, speed measuring and non-destructive detection. The magnetic sensors are primarily made of semiconductor materials exhibiting the Hall effect and the magnetic materials possessing anisotropic magnetoresistance (AMR). Both materials suffer from an inadequacy of sensitivity to magnetic fields. As the spintronics developed since 1988, the magnetic sensors built upon giant magnetorsistance [GMR] effect and tunnel magnetoresistance [TMR] have gained wider attention. Magnetic sensors based on spintronics materials have become popular for two reasons. One reason is that they are more sensitive. The other reason is that the techniques for making devices implementing the GMR and the TMR effect are compatible with those for making stable semiconductor products. Thus, the magnetic sensors promise a huge demand because of their extensive industrial applications.
The present technique in the industry for manufacturing GMR and TMR magnetic sensors (e.g. the magnetic read head in a hard disk drive [HDD]) involves essentially an embedded permanent magnetic film. The presence of the permanent magnetic film makes sure that the magnetic moment of the free layer in spin value structure—the layer sensitive to external magnetic field—and that of the reference layer—the pinned layer—stay at right angles. In turn, the magnetoresistance of a nano-structured magnetic multi-layer or magnetic tunnel junction [MTJ] responds linearly to the applied field, and free from magnetic hysteresis. Unfortunately, to embed a permanent magnetic film in the GMR spin value structure and in the MTJ hugely drives up the complexity and the cost for producing the devices. Moreover, the devices made with the present art are not as compact as we want them to be.